Poly(vinyl butyral) (PVB) is commonly used in the manufacture of polymer sheets that can be used as interlayers in light-transmitting laminates such as safety glass or polymeric laminates. Safety glass often refers to a transparent laminate comprising a poly(vinyl butyral) sheet disposed between two sheets of glass. Safety glass often is used to provide a transparent barrier in architectural and automotive openings. Its main function is to absorb energy, such as that caused by a blow from an object, without allowing penetration through the opening or the dispersion of shards of glass, thus minimizing damage or injury to the objects or persons within an enclosed area.
Plasticized poly(vinyl butyral), whether in sheet or pellet form, inherently tends to stick to itself during storage or transportation. The strength of the self-adhesion of plasticized poly(vinyl butyral) can reach such levels that it is impossible to separate if the sheets or pellets were not refrigerated. This kind of severe self-adhesion is referred to as ‘blocking’ in the art of poly(vinyl butyral) manufacture. The nature of blocking creates great difficulties in the sheet handling during manufacture, transportation, and the lamination process. It also makes it extremely difficult to feed poly(vinyl butyral) pellets continuously into an extruder. Although many attempts have been made to ameliorate or eliminate blocking in poly(vinyl butyral), few have been successful at producing a poly(vinyl butyral) that both resists blocking and provides a poly(vinyl butyral) with the desired physical and optical characteristics (see, for example, WO 02/12356).
The continuous feeding of plasticized poly(vinyl butyral) pellets during extrusion, compounding, blending, or molding would offer significant advantages and convenience in terms of processing and cost. Accordingly, further improved compositions and methods are needed to enhance the manageability of poly(vinyl butyral) pellets without detrimentally affecting optical qualities and without requiring cumbersome refrigeration.